scholarly journals Development of a semi automated dual feed unit to produce FGM coatings using the HVOF thermal spray process

2014 ◽  
Vol 32 (1) ◽  
pp. 18
Author(s):  
K.A. Mamun ◽  
J. Stokes

The application of functionally graded materials (FGMs) is quite difficult, but thermal spray processes like Plasma spray have demonstrated their unique potential in producing graded deposits, where researchers have used twin powder feed systems to mix different proportions of powders. FGMs vary in composition and/or microstructure from one boundary (substrate) to another (top service surface), and innovative characteristics result from the gradient from metals to ceramics or non-metallic to metals. The present study investigates an innovative modification of a high velocity oxy-fuel (HVOF) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. Graded coatings enable gradual variation of the coating composition and/or microstructure, which offers the possibility of reducing residual stress build-up with in coatings. In order to spray such a coating, modification to a commercial powder feed hopper was required to enable it to deposit two powders simultaneously which allows deposition of different layers of coating with changing chemical compositions, without interruption to the spraying process. Various concepts for this modification were identified and one design was selected, having been validated through use of a process model, developed using ANSYS Flotran finite element analysis. In the current research the mixing of different proportions of powders were controlled by a computer using LabVIEW software and hardware, which allowed the control and repeatability of the microstructure when producing functionally graded coatings.

2016 ◽  
Vol 96 ◽  
pp. 370-376 ◽  
Author(s):  
Jiajing Pan ◽  
Shengsun Hu ◽  
Lijun Yang ◽  
Kunying Ding ◽  
Baiqing Ma

2016 ◽  
Vol 1138 ◽  
pp. 139-146 ◽  
Author(s):  
Ioan Aurel Perianu

Hard chrome plating is a process that has been in commercial production for over 50 years and which is a critical process associated with manufacturing and maintenance of parts in the industries. The paper presents aspects regarding the use of HVOF thermal spray process as an alternative for hard chrome plating.


Author(s):  
L. C. Casteletti ◽  
A. Lombardi Neto ◽  
D. T. de Macedo ◽  
L. B. Cruvinel ◽  
George Totten

Several types of powders can be deposited on metal alloys for property improvement using thermal spray processes. Aircraft grade 7075 aluminum alloy possesses good mechanical properties but poor wear and corrosion resistance. Thermal spray coatings can improve the poor wear performance of 7075 so that it is suitable for use in severe conditions by depositing a hard, wear-resisting layer over the base material. This can be done by a simple production process while maintaining the base material properties. Among the available coatings, cobalt-base superalloys, such as Stellites, provides excellent protection against corrosion and wear. However, the treatment must not deteriorate the substrate hardness. In the High Velocity Oxygen Fuel (HVOF) thermal spray process, the short resident time of the powder in the flame results in a relatively small temperature increase, which in turn results in a lower substrate temperature during the coating deposition. In the present work, HVOF thermal spray process was used to coat 7075-T3 aluminum alloy samples with Stellite 6 superalloy. This treatment resulted in layers of high hardness and improved wear performance while keeping the base material properties unchanged.


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